Several things come to mind in listing quickly the stumbling blocks to effective optical design/total system interfacing. They are: the presence of about five definitions for most optical requirement parameters; lack of communication; horrendous delays in making critical decisions; realizable vs practical requirements; and the way optical designers are educated. The last is perhaps the most difficult and controversial problem. At the August 1974 ,SPIE meeting on "Effective Systems Integration and Optical Design," Robert E. Hopkins (Tropel, Inc.) and Leonard H. Wald (Lockheed Missiles and Space Corporation) had a long public discussion on this subject. Although on the surface it appeared that they had agreed on virtually nothing, I feel they were completely in agreement on the idea that optical designers should have included within their education an apprenticeship program. It may be that Wald also felt that such a program should be applied, also, to the egineering types who eventually might become project engineers. Hopkins seemed to feel that an apprenticeship program could never be achieved, while Wald did not seem convinced of the impossibility.

In this issue we present a series of papers covering optical activities at The Perkin-Elmer Corporation. The company began as a strictly optical business in the late 1930s, and has grown rapidly and continuously ever since, expanding into electronics and into peripheral areas necessary for the undertaking of developmental tasks of ever-expanding scope. It has grown from a sales volume of only a few million dollars at the beginning of World War II to a current level of over $200 million. The scope of its optically oriented business has progressed from simple optical elements and process instruments to large scale electro-optical systems, such as is exemplified by the Large Space Telescope reported on in one of the accompanying papers.

The scientific objectives of the Large Space Telescope, currently in the preliminary design phase, are summarized in this paper. The conceptual design of the Optical Telescope Assembly (OTA) and system requirements introduced by the Scientific Instruments are also described. LST operations are characterized with emphasis on the fine pointing system, star acquisition, and image motion sensing. The LST is designed for 15 years of useful life, and the Shuttle Space Transportation System will permit earth return for maintenance and equipment updates every 2 to 3 years. Major advances in man's knowledge of the universe are expected to result from the Large Space Telescope.

A new method for controlling the shape of an optical mirror which does not require any reaction against a support structure is described. A computer analysis has been made for a sample case of a simple, thin disc, and the required distribution of control points established for direct control of the first ten terms of a Zernike polynominal expansion describing the surface shape.

A brief review of the history of the development of laser line-scanning sensors at Perkin-Elmer is given, culminating in the KA-98( ). This development, traced over the past 11 years by means of descriptions of a number of sensors, is characterized by a trend towards improved performance at lower cost, size, and weight. Earlier systems recorded directly onto photographic film, whereas later units employed magnetic video tape and the possibility of real-time data link transmission of the video signals. The most recent model, the KA-98( ), has just completed flight tests. This unit, intended for high-performance aircraft, incorporates a cw GaAs laser and a large field of view. Although originally developed for reconnaissance, these sensors are finding other remote sensing applications such as oil-slick detection.

An assembly of 14 diffraction limited collimators project beams, up to 12 in. (30.5 cm) in diameter, into the aperture of an aerial camera under test. USAG 1951 targets, both standard and Cos/Cos2 corrected, are provided for off-axis angles of 0° to 60°. The collimators, targets, and camera are mounted on a rigid, isolated, vertical frame, 29 ft. (880 cm) high and 28 ft. (850 cm) wide. The building and air-conditioning requirements are also discussed.

A brief review of the several types of interferometer is given. Four specific forms of instrument which are routinely used for interferometric testing at Perkin-Elmer are illustrated and described. A number of examples of interferograms obtained with each form of instrument are presented. The relationship of recent advanced developments to the actual practice of interferometry is indicated.

A new concept (the annular field optical system) makes it possible to avoid the extreme complexity of conventional projection mask alignment objectives. This has been done in a new, extremely simple, all-reflecting optical system that consists of two, concentric, spherical mirrors. A monolithic block consisting of three mutually perpendicular plane mirrors is used to fold the system into a configuration that makes possible an inherently synchronous, simple scanning arrangement. Partially coherent illumination is used to increase the effective MTF without decreasing the depth of focus.

OAO-Copernicus, launched August 21, 1972, is in its third year of successful operation. Its contributions to scientific knowledge are contained in over 37 scientific papers. Princeton University Observatory has expanded the Guest Investigator Program to include 56 programs by a total of 66 astronomers from 23 countries. Observing time is currently scheduled for twelve months in advance. The engineering features of the Perkin-Elmer-built telescope are surveyed in this paper. A digest of the scientific results and a bibliography of OAO-C related papers is given, and the nature of the investigations planned at the time of writing (September 1974) is summarized.

High aperture lenses of a triplet construction containing germanium lens elements and designed for the 8 to 13 micro-meter spectral bandwidth have been known for at least 10 years. Pilkington P.E. have recently been carrying out research into the aperture limitations of the basic triplet design. The following text describes a simple modification that can be made to an all-germanium triplet which raises its aperture from a typical f/0.75 to the very high aperture of f/0.55 without recourse to aspheric surfaces or loss of field-of-view. An achromatised design utilizing three elements of germanium and one of KRS 5 and achieving an aperture of f/0.5 8 is also described.

Because of the demand for better performance in optical systems, there is a continuing effort to find more efficient ways of producing optics. Perkin-Elmer's involvement in developing new techniques for the fabrication of aspheric and flat surfaces has resulted in the generation of three machining methods: (1) computer-controlled polishing of aspheric surfaces, (2) continuous polishing of flat surfaces, and (3) single-point diamond tool machining of spheres and flats by means of the Precision Surface Generator. Optical flats larger than 20 inches in diameter have been produced that are flat to better than A /8 peak to valley. The Precision Surface Generator has successfully produced metal mirrors of aluminum, copper, and brass.

The six papers that comprise the technical meat of this OTF section were presented originally at SPIE seminars, and will appear in the Proceedings volumes for those meetings. The papers by Kuttner, Marchant, Ose and Murata, Macdonald, and van Leunen were given at the SPIE-OSA seminar Image Assessment and Specification held in Rochester, New York in May 1974; the paper by Price is from the Effective Systems Integration and Optical Design seminar held at the SPIE annual meeting in San Diego, August 1974. They are here collected and reprinted in archival form, to embody a theme -standardization of objective measures of imaging performance. At least I would like to consider that a statement of the theme; but each author speaks for his own viewpoint.

American National Standards Institute committee PH3, Photographic Apparatus, has a task force group at work on a proposed draft standard for OTF. In order to prepare a standard useful to you on this complex and controversial subject, your task force is presently working on a three-part standard roughly falling into Theory, Methods, and Practice. It will be capable of quick updating using addenda covering, for example, such varied material as Procedures, Form for Presentation of Data, Recommended Practices, Standard Reference Lens(es) and Templates for Calibration, Maintenance, and Correlation of Equipment and Results, etc. The first part, Theory, has been completed by David Dutton. At this stage of the work your task force encourages and invites your comments on the approach; welcomes ideas and workers; solicits material; wants your input. It is not too late . . . you can contribute. More on OTF. At the SPIE seminar on Image Assessment and Specification, Rochester, New York, May 1974, an ad hoc committee of 15 participants concerned with OTF standards spontaneously formed to coordinate activity and interchange information. Members are from England, Japan, West Germany, Holland, and the United States. It is our hope that we will be better informed and prepare useful standards by this cooperative effort.

The Committee on Quality Assessment of Optical Systems, group of the German Standards Institution (DIN) is engaged in the standardization of OTF measurement technique. The state-of-the-art of MTF measurements and calculations shows an agreement of a few percent. This is the result of MTF measurements and calculations performed on two lenses by several laboratories in Germany and in England. Lens No. 1: f/3.2, f = 100 mm, infinite conjugate, angular field up to 12.9°, A = 546 nm, spatial frequencies up to 400 c/mm. Lens No. 2: f/5.6, f = 90 mm, infinite conjugate, angular field up to 45.1°, A = 546 nm, spatial frequencies up to 80 c/mm. The agreement obtained encourages MTF standardization and the use of MTF to describe the optical quality of image-form-ing systems. A report on the results of the committee's work is given. The work is divided into four parts: Sheet 1. Symbols, Definition, Mathematical Relations Sheet 2. Equipment Parameters Sheet 3. Practical Measurement Sheet 4. Evaluation and Representation of Measurement Results.

Although more research work over the past 35 years or so has gone into the assessment of lenses for aerial reconnaissance and survey than perhaps for any other photographic application, it is only comparatively recently that really objective techniques have begun to be brought into use in the production of air cameras.

A working group of the Japan Optical Engineering Research Association (JOERA) was organized in April, 1974 and has made a start for making Japanese OTF standards by 1976. This working group will make the draft for OTF standards such as 1) optical systems to be applied, 2) definition of OTF and MTF, 3) standard graphical representation of OTF and MTF, and 4) inspection standard for the accuracy of MTF measuring instruments.

This paper describes some of the results of an exercise conducted via the SIRA Group on Image Assessment and involving the inter-comparison of several different and independent OTF calculation programs. Ten laboratories throughout Europe and Japan performed calculations based on the specifica-tion of a particular wide-angle lens.

Three trends are at present apparent in image-evaluation methods. The first trend is to leave the OTF to the theoreticians and replace it by the measurement of imaging characteristics which cover the overall imaging performance of the device under test as completely as possible. In such cases the measuring methods and even the measuring equipment have to be specified.

In order to obtain the lens you want, or to design the lens desired by a customer, the lens must be thoroughly specified. Not only that, but the specifications must be understood the - same by all parties involved. Unfortunately, even though most terminology related to lens specifications and tolerances is well defined, there is still much ambiguity and lack of care in the use of these terms. In addition, there are many terms that are not universally used with a single meaning. This paper discusses some of the ambiguities and inconsistencies, with the aim of emphasizing the need for adequate definitions and standardized usage of optical terminology.

For protection purposes, coverslips, such as glass, plastic or fused silica, usually are applied to optically coated cells. The short-circuit current of the coated cells with covers is reported to decrease, compared with the short-circuit current for coated cells without covers. The loss in short-circuit current is generally attributed to the fact that the optical matching between the coating and the cover is not optimized. However, recent work on silicon solar cells with optical coatings (SiO, Si3N4) and plastic covers (FEP Teflon) at NASA-LEWIS shows no decrease in short-circuit current under air mass zero simulated sunlight conditions; in fact, short-circuit current shows an increase in Si3N4 coated cells with plastic covers. The measured covering factor, defined as the ratio of short-circuit current of FEP covered cells to the bare coated cells, is consistent with the calculated covering factor based on single-layer coating theory.

If a camera is to be used for the special purpose of recording periodic grid-like patterns, the range of spatial frequencies which it must handle is limited, and its imaging performance for a given range can be optimized by installing a suitably slotted mask inside the lens aperture. With this modification, a standard 35 mm single lens reflex camera has been found to resolve up to 600 lines/mm in both vertical and horizontal directions across the full format. The tuned response of this camera makes it well adapted for measuring lateral displacements of large incoherently lit structures by the moire grid technique. Some preliminary results are described, and the technique is compared to laser speckle photography.

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